1. Field of the Invention
The present invention relates to a solid-state laser apparatus comprising a plurality of solid-state materials each including an active solid-state medium.
2. Description of the Prior Art
Referring now to FIG. 37, it illustrates a side view of a prior art solid-state laser apparatus as disclosed in technical literature such as Solid-State Laser Engineering, Springer-Verlag, pages 119-120. In the figure, reference numeral 1 denotes a reflection mirror, 2 denotes a partial reflection mirror, and 3 denotes a solid-state material including an active solid-state medium. In the case of a YAG laser, Nd:YAG (Nd:Yttrium Aluminum Garnet) is a solid-state material doped with Nd as an active solid-state material. Furthermore, reference numeral 4 denotes a pumping light source such as a semiconductor laser including GaAlAs as a major constituent thereof, 5 denotes a power supply which drives the pumping light source 4, 6 denotes a focus lens, 7 denotes a laser beam generated in a laser cavity constructed by the mirrors 1 and 2, 10 denotes an optical coating on the mirror 1 which serves to totally reflect the laser beam 7 and totally transmit incident light from the semiconductor laser 4, 70 denotes a laser beam which is extracted out of the laser cavity by the partial reflection mirror 2, and 100 denotes a base.
Next, the description will be directed to the operation of the prior art laser apparatus. When the power supply 5 by the light source is introduced into an end of the solid-state material 3 by the focus lens 6. Then, the pumping light which enters into the solid-state material 3 excites the active solid-state medium to produce a laser amplifying medium. Spontaneous emission light emitted by the laser amplifying medium travels back and forth within the laser cavity constructed by the mirrors 1 and 2 and is amplified during the travel. Furthermore, the directivity of the laser beam 7 is increased during the travel. When the power of the laser beam reaches a certain value, the laser beam is extracted out of the laser cavity as the laser beam 70.
Thus, such a prior art solid-state laser apparatus having the above-mentioned structure suffers from a problem that it cannot generate a high-power and high-quality laser beam when it is pumped by a high-power pumping light source. It is presumed that birefringence generated within the solid-state material due to thermal deformations causes a reduction in laser beam quality. However, the detailed mechanism to cause such a reduction has been unknown.